A cryogenic fluid, typically LPG or LNG, has a very low temperature at ambient pressure when stored as a liquid. If this liquid is spilled at or in a vessel all equipment in the vicinity of the spilled liquid will be cooled down to the boiling temperature of the liquid, which for LPG can be typically −50 degrees C. and for LNG typically −164 degrees C. Most vessels and equipment are built of carbon steel that will turn brittle and loose its structural strength at cryogenic temperatures.
The cryogenic liquid is maintained at or close to its boiling point at low temperature and any contact with other materials at a higher temperature will result in transfer of heat from that material to the liquid with consequently boil-off of liquid and cool down of the material. The liquid is therefore normally stored in well insulated pipes and tanks and all transfer is carried out with dedicated equipment and according to pre-determined and approved procedures to reduce the risk of spill and accidents.
When transferring a cryogenic fluid there is in several cases a need for a flexible joint for the fluid transfer channel. Having a joint gives the potential hazard of spillage of the fluid, having a flexible joint gives an increased risk of spillage since any seal in the flexible joint will experience a dynamic situation.
When transferring a cryogenic fluid or other hazardous fluid, this involves a potential risk for personnel in the vicinity of the joint. Any human exposure to the fluid, as liquid or cold gas may result in serious injury or death. Protection of personnel can be achieved by either prohibiting personnel to enter the area when cold media is present and can leak out, or by use of adequate protective equipment. At this time protective equipment is limited to space suits and similar clothing which by nature is either prohibitive expensive or not available at such sites. As a general rule personnel should therefore not be admitted to enclosed space where there is a possibility that for instance LNG may escape (from for instance rotating equipment or flanged connections). Equipment inside such space must therefore be remotely operated and monitored and all containers with cryogenic liquid must be drained and inerted before personnel can enter.
However, there is a need for a flexible joint for transferral of a for instance cryogenic fluid, which gives increased safety. There are known some flexible joints for instance described in GB1381902 or GB2337568. However, these known solutions do not give the needed flexibility and security. There are also described flexible joints in EP 0718537 and U.S. Pat. No. 6,328,347.
An object of the present invention is to provide a flexible joint for transfer of a fluid as for instance a cryogenic fluid, which is safer in case of spillage. It is an object to provide a joint with flexibility about more than one axis. It is a further object to provide a joint without spillage of the transferred fluid.
The joint as defined in the accompanying claims fulfils the above mentioned object.